Presenter: Andrew Wittenberg (NOAA GFDL)

Description:
Global coupled GCMs are essential tools to foretell future climate risks associated with the El Niño / Southern Oscillation (ENSO). Yet longstanding model biases in both small-scale processes and the emergent coupled climate state can alter the simulation of ENSO's dynamics, impacts, and responses to climate change. Here we describe recent advances at NOAA's Geophysical Fluid Dynamics Laboratory (GFDL) — including refined model resolution, enhanced physical parameterizations, large ensemble simulations, interpretable bias corrections, and improved diagnostics. These advances have yielded better ENSO simulations, with more realistic patterns, amplitudes, spectra, seasonal timing, inter-event diversity, mechanisms, and teleconnections. They also provide more useful climate information, and show different sensitivities to climate change. GFDL is deeply engaged in international efforts to develop community-sourced metrics, emergent constraints, and machine learning approaches for ENSO, leveraging large ensemble simulations and inter-model diversity in ways that illuminate ENSO's responses to climate change. Together, these efforts are improving understanding of ENSO and its sensitivities to climate forcings and model biases — with important implications for the Tropical Pacific Observing System (TPOS), and for evaluating ENSO in climate simulations and projections.